A resolver, one of rotation position detectors, detects a rotation angle of a rotary machine using a phenomenon that when a coil on the excitation side is excited by an AC voltage, the phase or amplitude of an AC output voltage induced on a coil on the output side is changed depending on a rotation angle. The principle of operation is common to that of a transformer, but the resolver differs from the transformer in that the iron core of the transformer is divided into a rotor and stator. The resolver can be used even in a high-temperature, high-vibration environment and is trouble-free, further resistant to noise and widely used as a detector for equipment requiring high-level reliability.
Of resolvers, a brush-less resolver generally uses a rotary transformer instead of a conventional brush and slip ring as means for transmitting a signal to the rotor.
FIG. 7 shows a half section illustrating the structure of a conventional brush-less resolver. In the figure, the conventional brush-less resolver is mainly constructed of a detection section (hereinafter referred to as “resolver section”) including a stator made up of a stator resolver iron core 131 and a stator resolver coil 132, and a rotor made up of a rotor resolver iron core 141 and a rotor resolver coil 142, a stator transformer made up of a stator transformer 151 and stator transformer coil 152, and a rotary transformer (hereinafter referred to as “transformer section”) made up of a rotor transformer rotor transformer 161 and a rotor transformer coil 162.
That is, the brush-less resolver is mainly constructed of a resolver section which obtains a voltage according to a rotation angle and a transformer section whose main purpose is to transmit signals to the rotor and when this is seen from a manufacturing aspect, the conventional brush-less resolver uses a cylindrical cutting transformer for the transformer section and uses a laminated iron core subjected to lamination machining for the resolver section, and in this way different components are used for various sections to manufacture the brush-less resolver, requiring the corresponding manufacturing cost and number of steps.
Furthermore, when the brush-less resolver is seen from the functional aspect, the stator transformer, rotor transformer, rotor iron core and stator iron core constitute a magnetic circuit, the transformer section made up of the stator transformer and rotor transformer carries only the function of transmitting a resolver excitation signal from the stator side to the rotor side in a non-contact manner, and the resolver section made up of the rotor iron core and resolver iron core has the original function of the resolver, that is, modulation of a resolver excitation signal corresponding to the rotation angle. Therefore, for the conventional brush-less resolver, the transformer section does not contribute to the original function of the resolver.
As described above, the conventional brush-less resolver uses different components for the transformer section and resolver section, which results in a problem that it is difficult to reduce the manufacturing cost. Furthermore, while the transformer section contributes to the realization of a brush-less structure of the resolver, the transformer section does not contribute to the modulation of a resolver excitation signal, but magnetic flux generated in the transformer section rather flows in the direction in which it is likely to interfere with the resolver section, which becomes one of causes of deterioration of the performance when seen from the aspect of the rotation angle detection performance of the resolver.
On the other hand, from the standpoint of expansion of the resolver application field, there are demands for further improvement of rotation angle detection accuracy, increase in the degree of freedom in selecting an axial double angle and increase in the degree of freedom in constructing the resolver in the brushless resolver.
In the case of a VR resolver, the rotor is constructed of only an iron core and has some effects in reductions of the number of parts and the number of pieces, but in the expansion of the degree of freedom in selecting the axial double angle, it is impossible to realize a resolver with an axial double angle 1 using the VR resolver characterized in that an angle signal corresponding to one rotation is obtained by one rotation of the resolver because the rotor has a shape eccentric with respect to the rotation center.
Based on all that described above, it is a problem to be solved by the present invention to provide a brush-less resolver capable of eliminating the problems of the above described conventional technology, allowing a cost reduction and obtaining an arbitrary axial double angle including axial double angle 1. That is, in the manufacturing aspect, it is a problem to be solved by the present invention to provide a brush-less resolver capable of reducing the number of parts and the number of pieces, reducing the cost, obtaining an arbitrary axial double angle including an axial double angle 1, increasing the degree of freedom of selecting an axial double angle, increasing the degree of freedom in an arbitrary resolver structure according to the use in the aspect of detection accuracy and reducing interference between the magnetic circuit on the excitation side and the magnetic circuit on the output side in the aspect of performance.